Although I've only been collecting for about five years, I've managed to find some very interesting minerals, mostly from geodes. When I first started collecting geodes and other rocks, I only collected from secondary sources i.e. creeks and rivers. Later on, I learned that the best rare minerals come from the solid limestone. It's a very exhausting task, but well worth it. Some of the minerals that I've collected in central Indiana include: quartz, calcite, barite, sphalerite, pyrite, aragonite, strontianite, millerite, jamborite, dolomite, gypsum, hematite, marcasite, pyrolusite, and siderite. Since I'm not a geologist, there's always a chance that I misidentified a mineral, so feel free to let me know so I can correct it. Good luck rock collecting!